I have an image that contains a circles at a specific location, and of a specific diameter. What I need to do is to be able to calculate random points within the circle, and then manipulate the pixels said points correlate to. I have the following code already:

And that works fine for finding all the points at the circumference of the circle, but I need all points from anywhere in the circle. If this doesn't make sense let me know and I will do my best to clarify.

If performance is an issue then one alternative solution is to generate a random position in a box with the width/height of your circle and then throw away any points that are not in the area of the circle.

The advantage of this method is that you are doing no cos/sin/sqrt functions, which depending on your platform may be a big speed saving.